### All High School Math Resources

## Example Questions

### Example Question #504 : Plane Geometry

Lines and are parallel. Which angle is congruent to angle ?

**Possible Answers:**

**Correct answer:**

When two lines are parallel, corresponding angles are congruent. Because we don't know if lines and are parallel, we can't make any conclusions about angles 2 and 3.

With the given information, we can ignore line , as it has no relation to angle . This leaves angles 1 and 4 as possible answers. Angle 4 will be congruent to angle , while angle 1 will supplement angle .

### Example Question #1 : How To Find The Angle Of Two Lines

Figure not drawn to scale.

In the figure above, APB forms a straight line. If the measure of angle APC is eighty-one degrees larger than the measure of angle DPB, and the measures of angles CPD and DPB are equal, then what is the measure, in degrees, of angle CPB?

**Possible Answers:**

114

33

40

66

50

**Correct answer:**

66

Let x equal the measure of angle DPB. Because the measure of angle APC is eighty-one degrees larger than the measure of DPB, we can represent this angle's measure as x + 81. Also, because the measure of angle CPD is equal to the measure of angle DPB, we can represent the measure of CPD as x.

Since APB is a straight line, the sum of the measures of angles DPB, APC, and CPD must all equal 180; therefore, we can write the following equation to find x:

x + (x + 81) + x = 180

Simplify by collecting the x terms.

3x + 81 = 180

Subtract 81 from both sides.

3x = 99

Divide by 3.

x = 33.

This means that the measures of angles DPB and CPD are both equal to 33 degrees. The original question asks us to find the measure of angle CPB, which is equal to the sum of the measures of angles DPB and CPD.

measure of CPB = 33 + 33 = 66.

The answer is 66.

### Example Question #1 : How To Find An Angle Of A Line

One-half of the measure of the supplement of angle ABC is equal to the twice the measure of angle ABC. What is the measure, in degrees, of the complement of angle ABC?

**Possible Answers:**

36

18

54

90

72

**Correct answer:**

54

Let x equal the measure of angle ABC, let y equal the measure of the supplement of angle ABC, and let z equal the measure of the complement of angle ABC.

Because x and y are supplements, the sum of their measures must equal 180. In other words, x + y = 180.

We are told that one-half of the measure of the supplement is equal to twice the measure of ABC. We could write this equation as follows:

(1/2)y = 2x.

Because x + y = 180, we can solve for y in terms of x by subtracting x from both sides. In other words, y = 180 – x. Next, we can substitute this value into the equation (1/2)y = 2x and then solve for x.

(1/2)(180-x) = 2x.

Multiply both sides by 2 to get rid of the fraction.

(180 – x) = 4x.

Add x to both sides.

180 = 5x.

Divide both sides by 5.

x = 36.

The measure of angle ABC is 36 degrees. However, the original question asks us to find the measure of the complement of ABC, which we denoted previously as z. Because the sum of the measure of an angle and the measure of its complement equals 90, we can write the following equation:

x + z = 90.

Now, we can substitute 36 as the value of x and then solve for z.

36 + z = 90.

Subtract 36 from both sides.

z = 54.

The answer is 54.

### Example Question #3 : Geometry

In the diagram, AB || CD. What is the value of a+b?

**Possible Answers:**

160°

None of the other answers.

140°

80°

60°

**Correct answer:**

160°

Refer to the following diagram while reading the explanation:

We know that angle b has to be equal to its vertical angle (the angle directly "across" the intersection). Therefore, it is 20°.

Furthermore, given the properties of parallel lines, we know that the supplementary angle to a must be 40°. Based on the rule for supplements, we know that a + 40° = 180°. Solving for a, we get a = 140°.

Therefore, a + b = 140° + 20° = 160°

### Example Question #1 : How To Find The Angle Of Two Lines

In rectangle *ABCD*, both diagonals are drawn and intersect at point *E*.

Let the measure of angle *AEB* equal *x* degrees.

Let the measure of angle *BEC* equal *y* degrees.

Let the measure of angle *CED* equal *z* degrees.

Find the measure of angle *AED* in terms of *x*,* y*, and/or* z*.

**Possible Answers:**

360 – *x* + *y* + *z*

180 – (*x* + *y* + *z*)

180 – *y*

180 – 2(*x* + *z*)

180 – 1/2(*x* + *z*)

**Correct answer:**

180 – 1/2(*x* + *z*)

Intersecting lines create two pairs of vertical angles which are congruent. Therefore, we can deduce that *y* = measure of angle *AED*.

Furthermore, intersecting lines create adjacent angles that are supplementary (sum to 180 degrees). Therefore, we can deduce that *x* + *y* + *z* + (measure of angle *AED*) = 360.

Substituting the first equation into the second equation, we get

*x* + (measure of angle *AED*) + *z* + (measure of angle *AED*) = 360

2(measure of angle *AED*) + *x* + *z* = 360

2(measure of angle *AED*) = 360 – (*x* + *z*)

Divide by two and get:

measure of angle *AED* = 180 – 1/2(*x* + *z*)

### Example Question #1 : Lines

Give another name for .

**Possible Answers:**

**Correct answer:**

Since the angle is called , it has vertex - the middle letter is *always* the vertex - and it is the union of rays and . Another name for is , since is also on that ray, so the angle can be said to be the union of and ; this makes a valid name for the angle.

and are not valid, since the middle letter is not vertex . is not valid, since and are on the same side of the angle. is not valid; an angle can be named using only its vertex only if it is the *only* angle in the diagram with that vertex, and that is not the case here.

### Example Question #2 : Lines

**Possible Answers:**

**Correct answer:**

Coresponding angles can be found when a line crosses two parallel lines. Angles 10 and 14 are equal, because corresponding angles are equal. Angles 14 and 13 are supplementary because together they form a straight line. If angles 10 and 14 are equal, then angles 10 and 13 must be supplementary as well.

### Example Question #2 : How To Find The Angle Of Two Lines

Two pairs of parallel lines intersect:

If A = 135^{o}, what is 2*|B-C| = ?

**Possible Answers:**

140°

160°

150°

180°

170°

**Correct answer:**

180°

By properties of parallel lines A+B = 180^{o}, B = 45^{o}, C = A = 135^{o}, so 2*|B-C| = 2* |45-135| = 180^{o}

### Example Question #6 : How To Find An Angle Of A Line

Two angles are supplementary and have a ratio of 1:4. What is the size of the smaller angle?

**Possible Answers:**

**Correct answer:**

Since the angles are supplementary, their sum is 180 degrees. Because they are in a ratio of 1:4, the following expression could be written:

### Example Question #1 : Geometry

Lines and are parallel. , , is a right triangle, and has a length of 10. What is the length of

**Possible Answers:**

Not enough information.

**Correct answer:**

Since we know opposite angles are equal, it follows that angle and .

Imagine a parallel line passing through point . The imaginary line would make opposite angles with & , the sum of which would equal . Therefore, .

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